An arbitrary waveform generator (AWG) is a form of electronic test equipment used to generate electrical waveforms with specified characteristics. Such electrical waveforms are commonly used, for instance, as test signals to evaluate the performance of electronic devices.
In one example application, an AWG generates an electrical waveform corresponding to a wireless communication signal. It then transmits the signal to a wireless device under test (DUT), which is monitored to determine whether it processes the signal properly. When generating the electrical waveform, the AWG may attempt to simulate real-world conditions in order to provide a rigorous test of the DUT's performance. Such real-world conditions may be simulated, for instance, by introducing, to the electrical waveform, impairments such as distortion, noise, or echoes. Accordingly, the monitoring of the DUT may include determining whether the DUT correctly recognizes the original electrical waveform in the presence of these impairments.
In a conventional AWG, the electrical waveform is synthesized off-line and then loaded into a memory of the AWG. Thereafter, when a test is performed, the AWG simply processes and outputs the pre-synthesized signal through defined channels. FIG. 1 is a diagram illustrating an example of such a conventional AWG.
Referring to FIG. 1, an AWG 100 comprises a digital waveform memory 105 and a plurality of digital-to-analog converters (DACs) 110. Digital waveform memory 105 receives and stores a digital waveform synthesized by a software program 115, which is typically implemented on a platform independent of AWG 100.
During typical usage, a user defines the digital waveform in software program 115, which may reside in a personal computer (PC), for example. The user then downloads the digital waveform from software program 115 to AWG 100, where it is stored in digital waveform memory 105. Subsequently, the user may control AWG 100 to convert the digital waveform into an analog waveform, which may be accomplished by outputting the digital waveform from memory 105 to DACs 110 and then performing digital-to-analog conversion with DACs 110. The analog waveform may then be transmitted to a DUT, either wirelessly or through wired connections.
The digital waveform typically comprises a plurality of time-dependent digital values representing voltages of the waveform. For instance, a digital waveform having a duration of 1 microsecond and a sample rate of 1 sample per 16 picoseconds may comprise 62.5k digital values each representing a voltage. The voltages may be defined by software program 115 to correspond to any arbitrary signal property, e.g., a high level, a low level, a rise time, an overshoot, an undershoot, etc.
The digital waveform may be designed and/or modified arbitrarily by a user with the aid of tools provided within software program 115. However, such design and/or modification must occur off-line. In other words, once the digital waveform is stored in digital waveform memory 105 of AWG 100, it remains fixed and static during generation of the analog waveform. Accordingly, any further modification of waveform characteristics requires another round of off-line re-synthesis of the digital waveform and downloading into digital waveform memory 105, which can take a significant amount of time.
Depending on download speed, waveform length, and/or memory depth of AWG 100, the download process may take a long time. Consequently, it may be prohibitively costly to generate different digital waveforms for a variety of different conditions, such as varying signal impediments (e.g., noise, echo, distortion), modulation formats, etc., due to the need to repeatedly perform the off-line re-synthesis.